Press shoe for extended nip press for dewatering a fiber web

Abstract

An extended nip press for the dewatering of a fiber web has an endless flexible press element, like a press jacket or press belt. A press shoe has a concave slide surface for the flexible press element, and the slide surface is adapted to the curve of a backing roll. The shoe is displaceable toward the backing roll in order to press the pressing element against it. A stationary shoe bed, which is detachably connected to a stationary support, has a depression which is provided with a packing and receives the press shoe to form a pressure chamber so that the shoe bed and the press shoe form a cylinder-piston unit. The press shoe is coupled to the shoe bed by means of at least one connecting element. The connecting element is spring biased with respect to the shoe bed and may itself be flexible or be flexibly moved to permit the radial displacement as well as the tilting of the press shoe relative to the shoe bed.

What is claimed is: 
     
       1. An extended nip press for dewatering a fiber web, the press comprising: a rotatable backing roll;   a press shoe having a concave slide surface generally adapted to the shape of and opposable to the periphery of the backing roll;   an endless flexible press element between the press shoe slide surface and the backing roll, and the press shoe being displaceable toward the backing roll for pressing the press element toward the backing roll;   a stationary shoe bed, including a depression opening to the press element, the depression having and being defined by a periphery and a bottom, the press show having a shape generally corresponding to the periphery of the depression and being received in the depression and being displaceable with respect to the depression and the shoe bed;   further comprising a stationary support for supporting the shoe bed stationary with respect to rotation of the backing roll and with respect to displacement of the press shoe, and means detachably connecting the shoe bed to the support;   means in the shoe bed defining a pressure chamber in the depression beneath the press show, whereby the shoe bed and the press shoe together form a cylinder-piston unit with the press show being displaceable with respect to the shoe bed;   at least one connecting element disposed between the shoe bed, and the side of the press shoe opposite the side with the slide surface thereon, for coupling the press shoe to the shoe bed, the connecting element comprising a flexible part structured to permit both displacement of the press shoe toward and away from the backing roll and tilting of the press shoe in any desired direction relative to the shoe bed in both the machine direction and the cross-machine direction.   
     
     
       2. The extended nip press of claim 1, wherein the connecting element includes means for urging the press shoe to be displaced with respect to the shoe bed and the backing roll. 
     
     
       3. The extended nip press of claim I, wherein the connecting element includes means for normally biasing the press shoe into the depression. 
     
     
       4. The extended nip press of claim 1, wherein the press element is a flexible endless jacket which endlessly passes over the slide surface of the press shoe. 
     
     
       5. The extended nip press of claim 1, wherein the means defining the pressure chamber in the depression comprises a packing for the depression at the periphery of the depression and extending into contact with the press shoe while permitting the press shoe to be displaced and tilted with respect to the shoe bed. 
     
     
       6. The extended nip press of claim 1, wherein the shoe bed has an opening therein at the connecting element, and the connecting element extends from the press shoe, through the pressure chamber and into the opening in the shoe bed. 
     
     
       7. The extended nip press of claim 6, wherein the opening through the shoe bed terminates on a side of the shoe bed which is outside the pressure chamber, and the connecting element having a -head thereon with a respective first stop surface such that displacement of the press shoe displaces the connecting element for moving the first stop surface against the side of the shoe bed, and the side of the shoe bed defines a second stop surface for cooperating with the first stop surface to limit the movement of the connecting element relative to the shoe bed. 
     
     
       8. The extended nip press of claim 7, further comprising means for sealing the opening through the shoe bed in pressure tight manner with the connecting element passing through the opening. 
     
     
       9. The extended nip press of claim 8, wherein sealing means comprises a flexible sealing ring which rests against the connecting element and the press bed. 
     
     
       10. The extended nip press of claim 1, wherein the connecting element extends from the press shoe, through the pressure chamber in the depression, and into the bottom of the depression of the shoe bed, and the connecting element being held in the shoe bed in a manner permitting displacement of the press shoe with respect to the shoe bed. 
     
     
       11. The extended nip press of claim 10, wherein the flexible part of the connecting element comprises a flexible bar. 
     
     
       12. The extended nip press of claim 6, further comprising biasing means at the connecting element having a spring force which is directed to counteract the pressure prevailing in the pressure chamber, the biasing means acting on the connecting element for moving the connecting element to urge the press shoe against the pressure prevailing in the pressure chamber. 
     
     
       13. The extended nip press of claim 1, further comprising a cylinder-piston unit connected with the connecting element, wherein the connecting element comprises the piston of the cylinder-piston unit, and the cylinder being connected to cause the pressure in the cylinder to exert a pressure on the connecting element which counteracts the pressure in the pressure chamber that is acting on the press shoe. 
     
     
       14. An extended nip press for dewatering a fiber web, the press comprising: a rotatable backing roll;   a press shoe having a concave slide surface generally adapted to the shape of and opposable to the periphery of the backing roll;   an endless flexible press element between the press shoe slide surface and the backing roll, and the press shoe being displaceable toward the backing roll for pressing the press element toward the backing roll;   a stationary shoe bed, including a depression opening to the press element, the depression having and being defined by a periphery and a bottom, the press shoe having a shape generally corresponding to the periphery of the depression and being received in the depression and being displaceable with respect to the depression and the shoe bed;   means in the shoe bed defining a pressure chamber in the depression beneath the press shoe, whereby the shoe bed and the press shoe together form a cylinder-piston unit with the press shoe being displaceable with respect to the shoe bed;   at least one connecting element extending between and coupling the press shoe to the shoe bed, the connecting element comprising a flexible part structured to permit both displacement of the press shoe toward and away from the backing roll and tilting of the press shoe in any desired direction relative to the shoe bed in both the machine direction and the cross-machine direction;   wherein the shoe bed has an opening therein at the connecting element, and the connecting element extends from the press shoe, at the side of the press shoe opposite the side with the slide surface thereon, through the pressure chamber and into an opening in the shoe bed;   wherein the opening through the shoe bed terminates on a side of the shoe bed which is outside the pressure chamber, and the connecting element has a head thereon with a respective first stop surface such that displacement of the press shoe displaces the connecting element for moving the first stop surface against the side of the shoe bed, and the side of the shoe bed defines a second stop surface for cooperating with the first stop surface to limit the movement of the connecting element relative to the shoe bed; and   further comprising means normally biasing the connecting element for moving the first and second stop surfaces apart and for normally biasing the press shoe into the depression, at least in the vicinity of the connecting element.   
     
     
       15. An extended nip press for dewatering a fiber web, the press comprising: a rotatable backing roll;   a press shoe having a concave slide surface generally adapted to the shape of and opposable to the periphery of the backing roll;   an endless flexible press element between the press shoe slide surface and the backing roll, and the press shoe being displaceable towrd the backing roll for pressing the press element toward the backing roll;   a stationary shoe bed, including a depression opening to the press element, the depression having and being defined by a periphery and a bottom, the press shoe having a shape generally corresponding to the periphery of the depression and being received in the depression and being displaceable with respect to the depression and the shoe bed;   means in the shoe bed defining a pressure chamber in the depression beneath the press shoe, whereby the shoe bed and the press shoe together form a cylinder-piston unit with the press shoe being displaceable with respect to the shoe bed;   at least one connecting element extending between and coupling the press shoe to the shoe bed, the connecting element comprising a flexible part structured to permit both displacement of the press shoe toward and away from the backing roll and tilting of the press shoe in any desired direction relative to the shoe bed in both the machine direction and the cross-machine direction;   wherein the shoe bed has an opening therein at the connecting element, and the connecting element extends from the press shoe, at the side of the press shoe opposite the side with the slide surface thereon, through the pressure chamber and into an opening in the shoe bed;   wherein the opening through the shoe bed terminates on a side of the shoe bed which is outside the pressure chamber, and the connecting element has a head thereon with a respective first stop surface such that displacement of the press shoe displaces the connecting element for moving the first stop surface against the side of the shoe bed, and the side of the shoe bed defines a second stop surface for cooperating with the first stop surface to limit the movement of the connecting element relative to the shoe bed; and   further comprising means for sealing the opening through the shoe bed in pressure tight manner with the connecting element passing through the opening; and   wherein the means for sealing the opening in the shoe bed comprises a pot surrounding the head of the connecting element, and the pot being sealed to the shoe bed.   
     
     
       16. An extended nip press for dewatering a fiber web, the press comprising: a rotatable backing roll;   a press shoe having a concave slide surface generally adapted to the shape of and opposable to the periphery of the backing roll;   an endless flexible press element between the press shoe slide surface and the backing roll, and the press shoe being displaceable toward the backing roll for pressing the press element toward the backing roll;   a stationary shoe bed, including a depression opening to the press element, the depression having and being defined by a periphery and a bottom, the press shoe having a shape generally corresponding to the periphery of the depression and being received in the depression and being displaceable with respect to the depression and the shoe bed;   means in the shoe bed defining a pressure chamber in the depression beneath the press shoe, whereby the shoe bed and the press shoe together form a cylinder-piston unit with the press shoe being displaceable with respect to the shoe bed;   at least one connecting element extending between and coupling the press shoe to the shoe bed, the connecting element comprising a flexible part structured to permit both displacement of the press shoe toward and away from the backing roll and tilting of the press shoe in any desired direction relative to the shoe bed in both the machine direction and the cross-machine direction;   wherein the shoe bed has an opening therein at the connecting element, and the connecting element extends from the press shoe, at the side of the press shoe opposite the side with the slide surface thereon, through the pressure chamber and into an opening in the shoe bed;   wherein the opening through the shoe bed terminates on a side of the shoe bed which is outside the pressure chamber, and the connecting element has a head thereon with a respective first stop surface such that displacement of the press shoe displaces the connecting element for moving the first stop surface against the side of the shoe bed, and the side of the shoe bed defines a second stop surface for cooperating with the first stop surface to limit the movement of the connecting element relative to the shoe bed;   further comprising means for sealing the opening through the side bed in pressure tight manner with the connecting element passing through the opening;   wherein the sealing means comprises a flexible sealing ring which rests against the connecting element and the press bed; and   further comprising a low pressure region at the shoe bed and a relief groove communicating between the opening and the low pressure region.   
     
     
       17. An extended nip press for dewatering a fiber web, the press comprising: a rotatable backing roll;   a press shoe having a concave slide surface generally adapted to the shape of and opposable to the periphery of the backing roll;   an endless flexible press element between the press shoe slide surface and the backing roll, and the press shoe being displaceable toward the backing roll for pressing the press element toward the backing roll;   a stationary shoe bed, including a depression opening to the press element, the depression having and being defined by a periphery and a bottom, the press shoe having a shape generally corresponding to the periphery of the depression and being received in the depression and being displaceable with respect to the depression and the shoe bed;   means in the shoe bed defining a pressure chamber in the depression beneath the press shoe, whereby the shoe bed and the press shoe together form a cylinder-piston unit with the press shoe being displaceable with respect to the shoe bed;   at least one connecting element extending between and coupling the press shoe to the shoe bed, the connecting element comprising a flexible part structured to permit both displacement of the press shoe toward and away from the backing roll and tilting of the press shoe in any desired direction relative to the shoe bed in both the machine direction and the cross-machine direction;   wherein the flexible part of the connecting element is in the form of a rope.   
     
     
       18. An extended nip press for dewatering a fiber web, the press comprising: a rotatable backing roll;   a press shoe having a concave slide surface generally adapted to the shape of and opposable to the periphery of the backing roll;   an endless flexible press element between the press shoe slide surface and the backing roll, and the press shoe being displaceable toward the backing roll for pressing the press element toward the backing roll;   a stationary shoe bed, including a depression opening to the press element, the depression having and being defined by a periphery and a bottom, the press shoe having a shape generally corresponding to the periphery of the depression and being received in the depression and being displaceable with respect to the depression and the shoe bed;   means in the shoe bed defining a pressure chamber in the depression beneath the press shoe, whereby the shoe bed and the press shoe together form a cylinder-piston unit with the press shoe being displaceable with respect to the shoe bed;   at least one connecting element extending between and coupling the press shoe to the shoe bed, the connecting element comprising a flexible part structured to permit both displacement of the press shoe toward and away from the backing roll and tilting of the press show in any desired direction relative to the shoe bed in both the machine direction and the cross-machine direction,   further comprising an auxiliary cylinder-piston unit connected with the connecting element, wherein the connecting element comprises the piston of the auxiliary cylinder-piston unit, and the cylinder being connected to cause the pressure in the cylinder to exert a pressure on the connecting element which counteracts the pressure in the pressure chamber that is acting on the press shoe;   wherein the cylinder of the auxiliary cylinder-piston unit is fastened on the shoe bed; the cylinder defining the first of a pair of stop surfaces and the piston defining the second of the pair of stop surfaces, which surfaces are brought together by displacement of the press shoe out of the depression to limit the stroke of the press shoe out of the depression.   
     
     
       19. The extended nip press of claim 18, wherein the auxiliary cylinder-piston unit is double acting, with the piston being so placed in the cylinder of the auxiliary cylinder-piston unit that the piston and the attached connecting element may be selectively acted upon to counteract the pressure prevailing in the pressure chamber and to selectively act on the pressure shoe in the same direction as the pressure prevailing in the pressure chamber. 
     
     
       20. A press shoe and shoe bed combination for use in an extended nip press, the combination comprising: a press shoe having a concave slide surface generally adapted to the shape of the periphery of a backing roll, the press shoe being displaceable toward the backing roll for the slide surface to press a press element toward the backing roll;   a stationary shoe bed including an open depression, the depression having and being defined by a periphery and a bottom, the press shoe having a shape generally corresponding to the periphery of the depression and being received in the depression and being displaceable with respect to the depression and the shoe bed;   further comprising a stationary support for supporting the shoe bed stationary with respect to rotation of the backing roll and with respect to displacement of the press shoe, and means detachably connecting the shoe bed to the support;   means in the shoe bed defining a pressure chamber in the depression beneath the press shoe, whereby the shoe bed and the press shoe together form a cylinder-piston unit with the press shoe being displaceable with respect to the shoe bed;   at least one connecting element disposed between the shoe bed, and the side of the press shoe opposite the side with the slide surface thereon, for coupling the press shoe to the shoe bed, the connecting element comprising a flexible part structured to permit both displacement of the press shoe toward and away from the backing roll and tilting of the press shoe in any desired direction relative to the shoe bed in both the machine direction and the cross-machine direction, the connecting element extending from the press shoe, through the pressure chamber in the depression, and into the bottom of the depression of the shoe bed, and the connecting element being held in the shoe bed in a manner permitting displacement of the press shoe with respect to the shoe bed.   
     
     
       21. The combination of claim 20, wherein the means defining the pressure chamber in the depression comprises a packing for the depression at the periphery of the depression and extending into contact with the press shoe while permitting the press shoe to be displaced and tilted with respect to the shoe bed. 
     
     
       22. The combination of claim 20, wherein the shoe bed has an opening therein at the connecting element, and the connecting element extends from the press shoe, through the pressure chamber and into the opening in the shoe bed. 
     
     
       23. The combination of claim 22, wherein the opening through the shoe bed terminates on a side of the shoe bed which is outside the pressure chamber, and the connecting element having a head thereon with a respective first stop surface such that displacement of the press shoe displaces the connecting element for moving the first stop surface against the side of the shoe bed, and the side of the shoe bed defines a second stop surface for cooperating with the first stop surface to limit the movement of the connecting element relative to the shoe bed. 
     
     
       24. The combination of claim 23, further comprising means normally biasing the connecting element for moving the first and second stop surfaces apart and for normally biasing the press shoe into the depression, at least in the vicinity of the connecting element. 
     
     
       25. The combination of claim 23, further comprising means for sealing the opening through the shoe bed in pressure tight manner with the connecting element passing through the opening; wherein the means for sealing the opening in the shoe bed comprises a pot surrounding the head of the connecting element, and the pot being sealed to the shoe bed. 
     
     
       26. The combination of claim 23, further comprising means for sealing the opening through the shoe bed in pressure tight manner with the connecting element passing through the opening; wherein the sealing means comprises a flexible sealing ring which rests against the connecting element and the press bed; and further comprising a low pressure region at the shoe bed and a relief groove communicating between the opening and the low pressure region. 
     
     
       27. The combination of claim 20, wherein the flexible part of the connecting element is in the form of a rope. 
     
     
       28. The combination of claim 20, further comprising an auxiliary cylinder-piston unit connected with the connecting element, wherein the connecting element comprises the piston of the auxiliary cylinder-piston unit, and the cylinder being connected to cause the pressure in the cylinder to exert a pressure on the connecting element which counteracts the pressure in the pressure chamber that is acting on the press shoe; wherein the cylinder of the auxiliary cylinder-piston unit is fastened on the shoe bed; the cylinder defining the first of a pair of stop surfaces and the piston defining the second of the pair of stop surfaces which surfaces are brought together by displacement of the press shoe out of the depression to limit the stroke of the press shoe out of the depression.   
     
     
       29. The combination of claim 28, wherein the auxiliary cylinder-piston unit is double acting, with the piston being so placed in the cylinder of the auxiliary cylinder-piston unit that the piston and the attached connecting element may be selectively acted upon to counteract the pressure prevailing in the pressure chamber and to selectively act on the pressure shoe in the same direction as the pressure prevailing in the pressure chamber.